1. Field of the Invention
The invention relates to a press-fitting connector for plastic composite pipes which are comprised of an inner layer and an outer layer of plastic material and a middle layer of metal, preferably aluminum, wherein the press-fitting connector comprises a support member onto which the end of the composite pipe can be slipped against an insulating ring of plastic material and an outer collar of the press-fitting connector, wherein the end of the composite pipe can be secured by means of a press-fit sleeve.
2. Description of the Related Art
It is known from DE 44 41 373 C2 to use press-fitting connectors of this kind for connecting plastic composite pipes to other fixtures or fittings. The outer collar of these known press-fitting connectors is L-shaped in axial section, wherein the free leg of the outer collar extending axis-parallel has a cutout at several locations which extends radially and provides a visual control of the plastic composite pipe slipped onto the support member up to the stop (collar). In order to protect these radial cutouts against soiling, this area should be protected by means of a corresponding transparent plastic ring. The transparency of such a ring, which, however, is not mentioned in the cited prior art DE 44 41 373 C2, is necessary because of the desired visual control of the insertion position of the composite pipe. However, the visual control made possible by means of this ring is greatly impaired, in particular, at mounting locations that are difficult to access.
A further disadvantage of this known press-fitting connector is that the aluminum layer of the plastic-metal composite pipe can come into contact with a press-fitting connector which, in general, is made of brass, and such a contact should be prevented in order to protect against corrosion. This disadvantage is prevented in a sealing connection of plastic-metal-plastic composite pipes according to EP 0 611 911 A1 by an annular plastic part which is snapped into place on the end of the press-fit sleeve and which is configured such that its inner flange end covers the end face of the composite pipe and thus prevents contact of the exposed metal layer at the end face of the composite pipe with the brass fitting. In this embodiment, however, the visual control of the correct position of the composite pipe at the stop of the press-fitting connector is not possible.
It is an object of the present invention to develop a press-fitting connector for plastic composite pipes which provides visual control of the correct position of the composite pipe between the press-fitting connector and the press-fit sleeve as well as an insulation between the end face of the composite pipe and the fitting.
In accordance with the present invention, this is achieved in that an outer circumferential rib of the press-fitting connector has two diametrically opposed cutouts and that the insulation ring of plastic material is embodied like a curved spring washer curved in the direction toward the composite pipe twice convexly and twice concavely, wherein in the center of each convexly curved portion of the insulating ring an axis-parallel tongue is formed as a monolithic part which engages one of the cutouts of the outer circumferential rib of the press-fitting connector and projects partially from the corresponding cutout in the axis-parallel direction at the side of the outer circumferential rib facing away from the composite pipe, when the composite pipe is completely inserted up to the stop position between the support member and the press-fit sleeve.
The embodiment according to the invention of a press-fitting connector provides in any position an excellent visual control and optionally also a control by touch of the correct position of the composite pipe between the press-fitting connector and the press-fit sleeve when the springy insulating ring made of plastic material, which is curved like a curved spring washer, is flattened by the inserted composite pipe so that the tongues project in the axial direction from the cutouts of the outer circumferential rib of the press-fitting connector in a visible and touchable way. In this connection, it can also be easily detected if the composite pipe slips relative to the press-fitting connector during further processing of the pipe connection, for example, when starting the pressing process. Moreover, the insulating ring prevents the!direct contact of the end face of the composite pipe with the press-fitting connector.